Your logbook will record all days you enter. However, for the number of qualifying days, there must be at least 50% logged as master of the vessel.
For Example, if you have 100 days logged and 10 as master (90 as crew), then only 20 days will be "qualified" (10 master and 10 crew). If you then add 5 more days as master, then your qualified days will jump to 30 (15 as master and 15 as crew).
Also, some days don't qualify such as a dinghy sailing towards bareboat charter master.